1. Field of the Invention
This invention relates to a control device in a continuously variable transmission system (hereinafter referred to briefly as "CVT") used as a power transmission system in a vehicle, and more particularly to a control device used during acceleration of the vehicle.
2. Description of the Prior Art
In a control device in a CVT, an engine rotational speed, at which a required engine output can be obtained at the minimum fuel consumption rate, is set as a target engine rotational speed Ne', and a speed ratio e (=Nout/Nin, where Nout is a rotational speed on the output side of the CVT, and Nin a rotational speed on the input side of the CVT) is controlled such that an actual engine rotational speed Ne can be a target engine rotational speed Ne'. For example, in Japanese Patent Publication No. 58-184347, (Application No. 67362/1982), a shift speed of the CVT during acceleration is determined on the basis of a difference between Ne' and Ne. Since the difference between Ne' and Ne occurs during acceleration, the shift of the CVT is continuously performed.
However, since, during shift, the transmission efficiency of the CVT is low, the fuel consumption rate is deteriorated accordingly, and further, a target engine rotational speed Ne' is set at a high value, whereby, when the acceleration time period is lengthened at the time of the maximum throttle valve opening, undesirable noise level occurs.